<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    "use strict";
    let arr = [1, 2, 3, 4, 5];
    console.log(arr.length);
    console.log(arr.sort());
    console.log(arr.reverse());
    console.log(arr.concat(["a", "b", "c"]));
    console.log(arr.join("-"));
    let arr2 = [[1, 2], [3, 4], [5, 6]];
    console.log(arr2[1][1]);
</script>

</body>
</html>